The present invention relates generally to systems utilized to form in situ underground soil cement columns and other subterranean structures, wherein the systems combine mechanical cutting with a high pressure slurry jetstream to break down and mix subsoil and slurry. More particularly, the present invention provides a method and apparatus which achieves an extremely high level of turbulence in a region described herein as a “cyclonic mixing region.” The cyclonic mixing region enhances the efficiency of the mixing process.
The present invention represents a significant improvement over my prior patents that relate to various apparatus and methods for creating various types of soil cement structures underground. Those patents include U.S. Pat. Nos. 4,793,740; 4,958,962; 5,396,964; 5,890,844; 6,183,166; 6,241,426; 6,988,856 and 7,377,726, all of which are incorporated herein by reference.
A limitation of the prior art systems is the efficiency with which the combination of mechanical cutting combined with hydraulic mixing breaks down particles of underground subsoil. The present invention increases the efficiency of the process by creating for the first time a region which resembles a cyclone and in which tremendous amounts of turbulence are created to enhance the process of breaking down, mixing and fluidizing the underground material; this increased efficiency is most important in clay subsoil, such as the clay found in the Gulf Coast region of the United States. The increased efficiency of the present invention allows operation either at higher pressures and velocities with improved results or at lower pressures and lower velocities with the same results.
Another problem with many of the prior art systems is that the high pressure stream of cement slurry may impact the side wall of the hole being created. This impact can degrade the integrity of the hole in some types of soil by washing away portions of the side wall. A significant aspect of the present invention is to prevent this extremely high energy jet stream from hitting and degrading the side wall of the hole being formed. Another significant advantage of the invention is that, by preventing degradation of the side walls, a much higher injection pressure and velocity may be utilized.
A further disadvantage of the prior art systems is that, as the tool is being retracted from the hole, in some situations the tool interacts negatively with the side wall of the hole, causing small portions of the side wall to break off, weakening the integrity of the hole. The present invention overcomes that problem by including a smooth exterior surface which acts as a trowel to preserve the integrity of the side walls as the apparatus is withdrawn from the hole.
A primary object of the invention is to provide a cyclonic mixing region in a subterranean soil processing tool which produces an increased level of turbulence that increases the speed and effectiveness of the process of breaking down particles of under-ground subsoil, particularly clay, and mixing and fluidizing the particles of underground subsoil to form soil cement structures.
A further object of the invention is to provide a subterranean soil processing method and apparatus in which the high pressure stream of cement slurry is deflected and redirected into a direction in which the jetstream does not impact the side wall of the hole; this deflection of the jetstream away from the side wall of the hole allows the use of higher slurry pressures and velocities compared with the slurry pressures and velocities usable in prior art systems.
A further object of the present invention is to reduce the negative interaction with a soil processing tool with the side wall of the hole as the soil processing tool is being withdrawn from the hole; the present invention provides an exterior surface which tends to trowel and smooth the side wall of the hole as the soil processing tool is retracted upwardly out of the hole.
Further objects and advantages will become apparent from the following description and the drawings.